1. Field of the Invention
The present invention relates generally to interactive response systems, and more particularly to an interactive television system which provides interactive programming using compressed, digital data having more than one video signal on a broadcast channel, or a multiplexed signal within a digital format, or both.
The invention also relates to seamlessly switching between video signals while viewing a first video signal, even though the video signal switched to may be on a different broadcast channel, or on the same channel multiplexed with, the currently viewed video signal.
2. Description of the Prior Art
Interactive systems are well known in the art. By synchronizing parallel tracks of an information storage media, and relating the content of the various tracks, it was found that interactive activity could be simulated. For example, commonly owned Freeman, U.S. Pat. No. 4,602,279 discloses the use of a time synchronized multi-track audio tape to store educational conversations. One track is employed to relay educational interrogatories to a user, and the remainder of the tracks, selectable by a switching mechanism, are used to convey responsive messages.
These systems progressed to interactive television, wherein multiple broadcast or cable channels were switched in response to user selections to provide interactive operation. Commonly owned Freeman, U.S. Pat. No. 4,847,700 discloses an interactive television system wherein a common video signal is synched to a plurality of audio channels to provide content related to user selectable responses.
Commonly owned Freeman, U.S. Pat. No. 4,264,925 discloses the use of a conventional cable television system to develop an interactive system. Standard television channels with time synchronized content are broadcast to a plurality of users. Each user switches between channels responsive to interrogatories to provide interactivity.
These systems have been tailored to include memory functions so that the system can be more interactive, individually responsive, and so that customized messages may be given to the various categories of users responsive to informational queries. Freeman, U.S. Pat. No. 4,602,279 discloses the use of a memory to store demographic profiles of television viewers. This information is stored to be recalled later for providing target specific advertising, for example. Prior art interactive television systems were generally concerned with providing one signal (i.e. one video signal) per channel, whether the channel is on cable television, broadcast television, or a VCR. Because cable and broadcast television channel capacity is becoming limited as more and more cable channels are being utilized for conventional programming, and interactive systems of the type described require multiple channels, it is desirable to reduce the channel capacity required for such systems while still providing at least the same level of interactivity. Disadvantages of the prior art are overcome by the present invention which provides an interactive television system which employs multiple, time-synchronized, content-related video signals on one or more broadcast channels.